Contact Lens Spectrum Supplements

Special Edition 2017

Contact Lens Spectrum

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C O N T A C T L E N S S P E C T R U M S P E C I A L E D I T I O N 2 0 1 7 c l s p e c t r u m . c o m 14 Dr. Ramdass is a clinical researcher at the Vision Research Institute and adjunct faculty member at the Michigan College of Optom- etry (MCO). She has received travel funding from Paragon Vision Sciences and lecture or authorship honoraria from Wink Productions, Inc. and SynergEyes. The Vision Research Institute at MCO has received research fund- ing from Bausch + Lomb, Paragon Vision Sciences, SynergEyes, and Art Optical. CUSTOM SOFT S T E P H A N I E R A M DA S S, O D Under the rationale that ocular sagittal height plays an important role in soft lens fitting (Young, 1992; van der Worp, 2013), my colleagues and I were interested in evaluating whether the sagittal height of a sam- ple of commercially available soft lenses could be reported on. Measuring Samples The Optimec is830 is a spectral domain optical coherence tomog- left to equilibrate for five minutes at 20°C. The lens was then measured, across a single meridian for the spherical lenses in the sample. To measure the sagittal height of the contact lens, the lens edge was first detected. The geometric center of the lens was then found based on the edge-to-edge diameter, and the perpendicular distance from lens inner apex was calculated to give the posterior sagittal depth. The contact lens samples were selected at random; two identical param- eters of each design were measured for comparison purposes. In total, four different lens brands (8 lenses total), each at a power of –2.50D, were measured twice. Their known material, re- ported base curve (BC) and diam- eter (DIA), and measured sagittal heights (SH) are found in Table 1. Final Words Could we use this information to match the sagittal height of an eye to that of a contact lens? If so, we may be able to adopt a more tech- nical fitting philosophy to better fit our patients with soft contact lenses. Further studies are ongoing. CLS For references, please visit www. clspectrum.com/references and click on document #SE2017. raphy-based contact lens measure- ment system. It is capable of mea- surement in both air and saline for different samples. For measurement of samples in saline, steps were tak- en to control the temperature of the measurement fluid. All soft lenses were immersed in the measurement fluid (0.9% sa- line) in a glass vial at least 24 hours prior to measurements. The sample was then placed in the wet cell and ARE WE TOO GENERAL WHEN IT COMES TO SOFT LENS FITTING? W hen we determine soft lens wear candidacy, clinical considerations include, but are not lim- ited to, patient age, spectacle refraction, ocu- lar health, desired wear schedule, occupation, and lens care compliance history. Ironically, when it comes to which soft lens we place on a patient's eye, we often generalize our selec- tion to our favorite brand and a single base curve. Sure, this methodology appears to work on most of our patients, but what if there was another way to determine if failure was imminent and further, if custom soft lens param- eters may be indicated? LENS SAMPLE MATERIAL BC (mm) DIA (mm) AVERAGE SH (mm) STANDARD DEVIATION 1 Lotrafilcon A 8.4 13.8 3.606 0.009 2 Lotrafilcon A 8.4 13.8 3.604 0.008 3 Samfilcon A 8.5 14.2 3.824 0.016 4 Samfilcon A 8.5 14.2 3.852 0.006 5 Senofilcon A 8.8 14.0 3.483 0.024 6 Senofilcon A 8.8 14.0 3.474 0.003 7 Nelfilcon A 8.7 14.0 3.432 0.008 8 Nelfilcon A 8.7 14.0 3.429 0.008 STUDY RESULTS T A B L E 1

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